A disk drive, such as a magnetic disk drive, comprises a magnetic disk, spindle motor, magnetic head, and carriage assembly. The magnetic disk is disposed in a case. The spindle motor supports and rotates the disk. The magnetic head reads and writes data from and to the disk. The carriage assembly supports the head for movement relative to the disk. The carriage assembly comprises a pivotably supported arm and a suspension extending from the arm, and the magnetic head is supported on an extended end of the suspension. The head comprises a slider mounted on the suspension and a head section disposed on the slider. The head section comprises a recording head for writing and a reproduction head for reading.
Magnetic heads for perpendicular magnetic recording have recently been proposed in order to increase the recording density and capacity of a magnetic disk drive or reduce its size. In one such magnetic head, a recording head comprises a main pole configured to produce a perpendicular magnetic field, return or write/shield pole, and coil. The return pole is located on the trailing side of the main pole with a write gap therebetween and configured to close a magnetic path that leads to a magnetic disk. The coil serves to pass magnetic flux through the main pole.
To increase the recording density in the future, data must be recorded with a narrower track pitch. Therefore, the main pole of a recording head tends to become smaller and smaller. When the main pole is small, however, a pinning site of a magnetic domain wall is easily produced in it. Therefore, recording magnetic flux cannot be properly guided to the distal end of the main pole during signal recording, so that a magnetic field applied from the distal end of the main pole to a recording medium becomes unstable. Thus, the signal output becomes unstable, and the signal-to-noise ratio is degraded.